Wire rope

ABSTRACT

A wire rope having improved durability and that can be used in a medical device to be inserted into a patient&#39;s body. The wire rope includes a core wire and side wires. The core wire is a special metal element wire that has a hardness at an outer periphery in a cross-section thereof that is higher than that at a center in the cross-section thereof. The wire rope does not include grease.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of PCT/JP2016/063945 filed on May 11,2016, the contents of which are incorporated by reference herein intheir entirety.

BACKGROUND

The disclosed embodiments relate to a wire rope comprising multiplemetal element wires.

In a conventional wire rope, multiple metal element wires are twistedtogether to form the wire rope. In general, wire ropes have advantagessuch as excellent impact resistance and good flexibility as comparedwith a single metal element wire. Further, wire ropes are oftensubjected to repeated bending, and thus desirably have good durabilityunder such usage conditions.

For example, Japanese Patent Application Laid-Open No. 2004-327254describes an aluminum twisted wire (a wire rope) in which spaces betweentwisted wires inside an outermost aluminum twisted wire layer are filledwith grease to improve the life time of the wire rope (see FIG. 1 andthe like).

Further, Japanese Patent Application Laid-Open No. H08-144182 describesa twisted wire rope having an improved life time, which can be preparedby (1) forming an uneven surface on each surface of multiple metalelement wires, (2) forming element twisted wires by twisting themultiple metal element wires each having the uneven surface, (3)twisting the element twisted wires and then applying a resin coatingaround the twisted element twisted wires, and (4) filling spaces betweenthe resin coating and the element twisted wires with grease (see FIG. 2and others).

Further, Japanese Patent Application Laid-Open No. 2004-124342 describesan inner wire rope having an improved abrasion resistance and the like,which can be prepared by subjecting side strands to deforestationprocessing to make surface contacts between a core strand and the sidestrands, and sealing lubricating oil between the core strand and theside strands (see FIG. 1 and the like).

However, a step of grease filling is inevitably required whenmanufacturing the wire ropes described in Japanese Patent ApplicationsLaid-Open Nos. 2004-327254, H08-144182, and 2004-124342, althoughcontaining grease in the wire ropes can improve their durability.

Further, the wire ropes described in Japanese Patent ApplicationsLaid-Open Nos. 2004-327254, H08-144182, and 2004-124342 cannot be usedin medical devices to be inserted into a patient's body because thesewire ropes are filled with grease within the wire ropes. Therefore,there is a need to develop a wire rope having an improved durabilitywithout containing grease for use in medical devices.

SUMMARY

The disclosed embodiments have been developed to address the aboveproblem. An object of the disclosed embodiments is to provide a wirerope having improved durability without containing grease, and inparticular a wire rope with improved durability which can be used in amedical device to be inserted into a patient's body.

In order to achieve the above object, the disclosed embodiments includea wire rope comprising multiple metal element wires wound together, andin which the multiple metal element wires include at least one specialmetal element wire that has a first hardness at an outer periphery in across-section thereof that is higher than a second hardness at thecenter in the cross-section thereof. The special metal element wire canimpart improved durability to the wire rope without requiring the use ofgrease, enabling the wire rope to be used in a medical device.

As defined herein, a “special metal element wire” is a metal elementwire in which the hardness at the outer periphery of the metal elementwire is higher than at the center of the metal element wire.

The at least one special metal element wire may be arranged at thecenter of the wire rope. This can further improve the durability of thewire rope.

Moreover, the wire rope may consist only of the at least one specialmetal element wire and multiple side metal element wires in contact withthe at least one special metal element wire. This can further improvethe durability of the wire rope.

The at least one special metal element wire may have a circularcross-section, and the multiple side metal element wires may each havean approximately trapezoidal cross-section. The cross-section is“approximately trapezoidal” if it resembles a trapezoid having 4 definedsides, even if the sides and/or corners are partially or even completelycurved. This can even further improve the durability of the wire rope.

Furthermore, a bundled wire rope may be formed by twisting together aplurality of any one of the wire ropes discussed above. This can furtherimprove durability.

Moreover, the wire rope may comprise, at its center, a twisted wire inwhich multiple special metal element wires are twisted together. Thiscan improve the flexibility of the wire rope.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of a wire rope according to thedisclosed embodiments.

FIG. 2 shows a first hardness distribution in a cross-section of aspecial metal element wire.

FIG. 3 shows a second hardness distribution in a cross-section of aspecial metal element wire.

FIG. 4 shows a side view of a wire rope according to the disclosedembodiments.

FIG. 5 shows a cross-sectional view taken along line A-A in FIG. 4.

FIG. 6 shows a side view of a wire rope according to the disclosedembodiments.

FIG. 7 shows a cross-sectional view taken along line B-B in FIG. 6.

FIG. 8 shows a cross-sectional view of a wire rope according to thedisclosed embodiments.

FIG. 9 shows a cross-sectional view of a wire rope according to thedisclosed embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

Below, embodiments of the present invention will be described withreference to the drawings.

FIG. 1 shows a cross-sectional view of a wire rope according to thedisclosed embodiments. FIG. 2 shows a first hardness distribution of across-section of a special metal element wire used for the wire rope.FIG. 3 shows a second hardness distribution of a cross-section of aspecial metal element wire used for the wire rope.

With reference to FIG. 1, a wire rope 1 comprises a core wire 3 (whichcorresponds to the “special metal element wire”) located at the center,and 6 side wires 5 (5 a, 5 b, 5 c, 5 d, 5 e, and 5 f) wound around thecore wire 3.

The core wire 3 is a metal element wire having a circular cross-section.There is no particular limitation for the material of the core wire 3,but stainless steel is used for purposes of this discussion.

A peripheral part (outer periphery, or outer edge) of the core wire 3 ina cross-section has a higher hardness than a center of the core wire 3in the cross-section. That is, the core wire 3 is configured to have astructure where only the surface region (surface) of the core wire 3 ishardened, but the inside of the core wire 3 is not hardened. Thisstructure allows the core wire 3 to have both flexibility and improvedresistance to abrasion due to contact between the core wire 3 and theside wires 5.

Note that conventionally known methods such as swaging and wire drawingcan be used in order to obtain a metal element wire (e.g., the core wire3) in which a hardness of the peripheral part in a cross-section of themetal element wire is higher than that of the center in thecross-section.

Further, the hardness of the core wire 3 may increase in a second-orderfashion toward the outer periphery from the center in a cross-section ofthe core wire 3 as shown in FIG. 2, or may increase in a linear fashion.Alternatively, the core wire 3 may include a constant-hardness region inthe vicinity of the center of the core wire 3 that spans from the centerto an intermediate position of the core wire 3 in a cross-section, andthe hardness may increase from the intermediate position toward theouter periphery as shown in FIG. 3.

Note that the hardness described in FIGS. 2 and 3 is expressed in theVickers hardness as measured with a Vickers hardness meter, and has aunit of “HV.”

The hardness of the center of the core wire 3 in FIG. 2 is about 650 HV,while the hardness at the outer periphery is about 700 HV, showing adifference of 50 HV. The hardness of the core wire 3 in FIG. 3 isconstant at about 650 HV in the vicinity of the center of the core wire3, while it is about 700 HV at the outer periphery, showing a differenceof 50 HV.

Note that the experiments performed by the present applicantdemonstrated that the flexibility and abrasion resistance were improvedeven when the hardness at the center in a cross-section was only 550 HV,and the hardness at the outer periphery in the cross-section was only580 HV.

In contrast, the flexibility of the wire rope 1 was impaired and thedurability decreased when the hardness of the entire region in across-section of the core wire 3 was, for example, 700 HV.

The side wires 5 (5 a, 5 b, 5 c, 5 d, 5 e, and 5 f), which are metalelement wires each having a circular cross-section, are spirally woundaround the core wire 3 in the longitudinal direction. There is noparticular limitation for the material of the side wires 5 (5 a, 5 b, 5c, 5 d, 5 e, and 5 f) as well, but stainless steel is used for purposesof this discussion. Tungsten may also be used.

In the wire rope 1, the core wire 3 having a hardness of the peripheralpart in a cross-section higher than that of the center is arranged atthe center of the wire rope 1 such that the multiple side wires 5 (5 a,5 b, 5 c, 5 d, 5 e, and 5 f) all make contact with the core wire 3. Thiscan improve the durability of the wire rope 1.

Below, another wire rope of the disclosed embodiments will be describedwith reference to FIGS. 4 and 5. Throughout this disclosure,descriptions will be omitted for parts that have already been described,to which the same reference numbers will be assigned in the figures.FIG. 4 shows a side view of the wire rope, and FIG. 5 shows across-sectional view taken along line A-A in FIG. 4.

With reference to FIGS. 4 and 5, a wire rope 11 comprises a core wire 3located at the center of the wire rope 11, and 6 side wires 15 (15 a, 15b, 15 c, 15 d, 15 e, and 15 f) wound around the core wire 3.

The side wires 15 (15 a, 15 b, 15 c, 15 d, 15 e, and 15 f), which aremetal element wires each deforestation-processed into an approximatelytrapezoidal shape, are spirally wound around the core wire 3 in thelongitudinal direction. There is no particular limitation for thematerial of the side wires 15 (15 a, 15 b, 15 c, 15 d, 15 e, and 15 f),but stainless steel is used for purposes of this discussion. Tungstenmay also be used.

In the wire rope 11, the core wire 3 having a hardness of the peripheralpart in a cross-section higher than that of the center is arranged atthe center of the wire rope 11 such that the 6 side wires 15 (15 a, 15b, 15 c, 15 d, 15 e, and 15 f) each having an approximately trapezoidalcross-section all make surface contact with the core wire 3. The wirerope 11 has an approximately circular cross-sectional outer periphery.This can improve not only the torque transmissibility of the wire rope11 (the torque transmissibility to one end of a wire rope when the otherend of the wire rope is rotated), but also the durability of the wirerope.

FIG. 6 shows a side view of a wire rope according to the disclosedembodiments, and FIG. 7 shows a cross-sectional view taken along lineB-B in FIG. 6.

With reference to FIGS. 6 and 7, a wire rope 101 comprises the core wirerope 11 shown in FIGS. 4 and 5 located at the center, and 6 side wireropes 21, 31, 41, 51, 61, and 71 wound around the core wire rope 11.That is, the wire rope 101 is a bundled wire rope.

The side wire ropes 21, 31, 41, 51, 61, and 71 each have a similarstructure to that of the core wire rope 11, and are spirally woundaround the core wire rope 11 in the longitudinal direction.

That is, the side wire rope 21 comprises a core wire 3 a located at thecenter (which corresponds to the “special metal element wire”) and 6side wires 25 (25 a, 25 b, 25 c, 25 d, 25 e, and 25 f) wound around thecore wire 3 a; the side wire rope 31 comprises a core wire 3 b (whichcorresponds to the “special metal element wire”) located at the centerand 6 side wires 35 (35 a, 35 b, 35 c, 35 d, 35 e, and 35 f) woundaround the core wire 3 b; the side wire rope 41 comprises a core wire 3c (which corresponds to the “special metal element wire”) located at thecenter and 6 side wires 45 (45 a, 45 b, 45 c, 45 d, 45 e, and 45 f)wound around the core wire 3 c; the side wire rope 51 comprises a corewire 3 d (which corresponds to the “special metal element wire”) locatedat the center and 6 side wires 55 (55 a, 55 b, 55 c, 55 d, 55 e, and 55f) wound around the core wire 3 d; the side wire rope 61 comprises acore wire 3 e (which corresponds to the “special metal element wire”)located at the center and 6 side wires 65 (65 a, 65 b, 65 c, 65 d, 65 e,and 65 f) wound around the core wire 3 e; and the side wire rope 71comprises a core wire of 3 f (which corresponds to the “special metalelement wire”) located at the center and 6 side wires 75 (75 a, 75 b, 75c, 75 d, 75 e, and 75 f) wound around the core wire 3 f.

The wire rope 101 is formed by twisting a plurality of wire ropes, eachof which has arranged at its center a core wire having a hardness of theperipheral part in a cross-section higher than that of the center suchthat 6 side wires each having an approximately trapezoidal cross-sectionall make contact with the core wire, each wire rope being configured tohave an approximately circular cross-sectional outer periphery. This canfurther improve not only the torque transmissibility of the wire rope101 (the torque transmissibility to one end of a wire rope when theother end of the wire rope is rotated), but also the durability of thewire rope 101.

FIG. 8 shows a cross-sectional view of a wire rope 81 according to thedisclosed embodiments. The wire rope 81 comprises a core twisted wire 13located at the center, 4 inner side wires 82 arranged at the outside ofthe core twisted wire 13, and 8 outer side wires 85 wound around thecore twisted wire 13 and the inner side wires 82.

The core twisted wire 13 comprises 4 metal element wires (13 a, 13 b, 13c, and 13 d (each corresponds to the “special metal element wire”), andeach metal element wire has a circular cross-section. There is noparticular limitation for the material of the metal element wires (13 a,13 b, 13 c, and 13 d), but stainless steel is used for purposes of thisdiscussion.

Here, the metal element wires (13 a, 13 b, 13 c, and 13 d), whichconstitute the core twisted wire 13, each have a hardness of theperipheral part in a cross-section higher than that of the center in thecross-section. That is, each metal element wire (13 a, 13 b, 13 c, and13 d) has a structure in which only the surface of the metal elementwire is hardened, but the inside of the metal element wire is nothardened. Further, the core twisted wire 13 is formed by twisting fourof these metal element wires. This can improve the flexibility anddurability of the core twisted wire 13.

Moreover, 4 inner side wires 82 (82 a, 82 b, 82 c, and 82 d) arearranged at the outside of the core twisted wire 13. Each of the innerside wires 82 (82 a, 82 b, 82 c, and 82 d) has a circular cross-sectionand a diameter smaller than that of each metal element wire (13 a, 13 b,13 c, and 13 d) of the core twisted wire 13. Note that there is noparticular limitation for the material of the inner side wires 82 (82 a,82 b, 82 c, and 82 d), but stainless steel is used for purposes of thisdiscussion.

Further, 8 outer side wires 85 (85 a, 85 b, 85 c, 85 d, 85 e, 85 f, 85g, and 85 h), which are metal element wires each having a circularcross-section, are arranged at the outside of the core twisted wire 13and the inner side wires 82 (82 a, 82 b, 82 c, and 82 d). Note thatthere is no particular limitation for the material of the outer sidewires 85 (85 a, 85 b, 85 c, 85 d, 85 e, 85 f, 85 g, and 85 h), butstainless steel is used for purposes of this discussion.

In the wire rope 81, the core twisted wire 13 (formed by twisting 4metal element wires each having a hardness of the peripheral part in across-section higher than that of the central part) is arranged at thecenter. This can further improve the flexibility and durability of thewire rope 81.

FIG. 9 shows a cross-sectional view of a wire rope 91. The wire rope 91comprises a core twisted wire 23 located at the center, 4 inner sidewires 92 arranged at the outside of the core twisted wire 23, and 8outer side wires 95 wound around the core twisted wire 23 and the innerside wires 92.

The core twisted wire 23 comprises 4 metal element wires (23 a, 23 b, 23c, and 23 d, and each of the metal element wire has a circularcross-section. There is no particular limitation for the material of themetal element wires (23 a, 23 b, 23 c, and 23 d), but stainless steel isused for purposes of the discussion.

Here, among the metal element wires (23 a, 23 b, 23 c, and 23 d) of thecore twisted wire 23, the metal element wire 23 d has a hardness of theperipheral part in a cross-section higher than that of the center in thecross-section. That is, the metal element wire 23 d is configured tohave a structure in which only the surface of the metal element wire ishardened, but the inside of the metal element wire is not hardened (themetal element wire 23 d corresponds to the “special metal elementwire”). On the other hand, the metal element wires 23 a, 23 b, and 23 ceach have an approximately constant hardness profile throughout across-section.

Further, the core twisted wire 23 is formed by twisting the 4 metalelement wires. This can further improve the flexibility of the coretwisted wire 23.

Moreover, 4 inner side wires 92 (92 a, 92 b, 92 c, and 92 d) arearranged at the outside of the core twisted wire 23. Each of the innerside wires 92 (92 a, 92 b, 92 c, and 92 d) has a circular cross-sectionand a diameter smaller than that of each metal element wire (23 a, 23 b,23 c, and 23 d) of the core twisted wire 23. Note that there is noparticular limitation for the material of the inner side wires 92 (92 a,92 b, 92 c, and 92 d), but stainless steel is used for purposes of thisdiscussion.

Furthermore, 8 outer side wires 95 (95 a, 95 b, 95 c, 95 d, 95 e, 95 f,95 g, and 95 h), which are metal element wires each having a circularcross-section, are arranged at the outside of the core twisted wire 23and the inner side wires 92 (92 a, 92 b, 92 c, and 92 d). Note thatthere is no particular limitation for the material of the outer sidewires 95 (95 a, 95 b, 95 c, 95 d, 95 e, 95 f, 95 g, and 95 h), butstainless steel is used for purposes of this discussion.

In the wire rope 91, the core twisted wire 23 formed with the metalelement wires each having a hardness of the peripheral part in across-section higher than that of the central part is arranged at thecenter of the wire rope 91. This can improve the flexibility anddurability of the wire rope 91.

Although disclosed embodiments of wire ropes are described above, thepresent invention shall not be limited to these embodiments. The presentinvention can be practiced with various modifications made withoutdeparting from the scope of the present invention.

For example, as described above, the side wires 5, 15, 25, 35, 45, 55,65, and 75 in the wire ropes 1, 11, and 101 are each formed with 6 metalelement wires. The number of metal element wires is, however, notlimited to 6, and 3 or more may be sufficient.

Moreover, the core twisted wires 13 and 23 are described as being formedby twisting 4 metal element wires. The number of metal element wires is,however, not limited to 4, and two or more may be sufficient.

Moreover, the outer side wires 85 and 95 in the wire ropes 81 and 91each comprise 8 metal element wires. The number of metal element wiresis, however, not limited to 8, and any number may be used as long as thecore twisted wire 13 or 23 is covered.

Moreover, the inner side wires 82 and 92 are provided in the wire ropes81 and 91, but the inner side wires 82 and 92 may not be present.

What is claimed is:
 1. A wire rope comprising multiple metal elementwires wound together, wherein the multiple metal element wires includeat least one special metal element wire that has a first hardness at anouter periphery in a cross-section thereof that is higher than a secondhardness at a center in the cross-section thereof.
 2. The wire ropeaccording to claim 1, wherein the at least one special metal elementwire is arranged at a center of the wire rope.
 3. The wire ropeaccording to claim 2, wherein the multiple metal element wires consistof the at least one special metal element wire and multiple side metalelement wires in contact with the at least one special metal elementwire.
 4. The wire rope according to claim 3, wherein the at least onespecial metal element wire has a circular cross-section, and themultiple side metal element wires each have an approximately trapezoidalcross-section.
 5. A bundled wire rope formed by twisting together aplurality of the wire rope according to claim
 4. 6. The wire ropeaccording to claim 1, wherein: the at least one special metal elementwire comprises multiple special metal element wires, and a twisted wirein which the multiple special metal element wires are twisted togetheris arranged at a center of the wire rope.
 7. The wire rope according toclaim 1, wherein the wire rope contains no grease.